1. Field of the Invention
This invention relates to the making of electronic components such as semiconductor wafer VLSI and ULSI integrated circuit devices, and, more particularly, to a method for forming a robust barrier layer in the device interconnects with excellent step coverage, uniformity, low resistance and enhanced adhesion to CVD-copper and to the electronic components made by the method.
2. Description of Related Art
The demand for manufacturing semiconductor integrated circuit (IC) devices such as computer chips with high circuit speed, high packing density and low power dissipation requires the downward scaling of feature sizes in ultra-large-scale integration (ULSI) and very-large-scale integration (VLSI) structures. The trend to smaller chip sizes and increased circuit density requires the miniaturization of interconnect features which severely penalizes the overall performance of the structure because of increasing interconnect resistance and reliability concerns such as fabrication of the interconnects and electromigration.
In general, such structures use silicon wafers with silicon dioxide (SiO2) being the dielectric material and openings are formed in the SiO2 dielectric layer in the shape of vias and trenches which are then metallized forming the interconnects. Increased miniaturization is reducing the openings to submicron sizes (e.g., 0.2 micron and lower) and increasing the aspect ratio (ratio of the height of the opening to the width of the opening) of the features.
With the decrease of the design rule, copper gets more focus as a conducting material for the interconnect in ULSI and VLSI devices since it has lower resistivity and higher electromigration resistance than aluminum. Copper easily diffuses through silicon dioxide and silicon, however, and a robust barrier layer to prevent copper diffusion is required to encapsulate the copper interconnect.
Step coverage of the diffusion barrier is also critical for the interconnect. Normally, physical vapor deposition (PVD) does not produce enough material on the side wall of the contact hole or the via, and, as the minimum feature size decreases, this phenomenon gets more critical. On the other hand, chemical vapor deposition (CVD) offers much better step coverage on the side wall of the contact hole and so is the preferable method for the formation of the diffusion barriers. Furthermore, the diffusion barrier itself must be thin and uniform otherwise, the line resistance may be greater than the resistance of aluminum interconnects.
The prior art method for the formation of a diffusion barrier is to deposit a material such as TiN, TiNSi, or Ta, or TaN, or TaSiN by CVD or PVD. CVD copper on these barrier materials has poor adhesion, however, and the copper peels out during a process such as chemical mechanical planarization (CMP) or in the following integration process. PVD Ta and/or PVD TaN, which is the most common barrier in the prior art, is normally followed by PVD copper as a seed for the electro-plating of bulk copper to fill the feature. However, due to poor step coverage on the side wall of the contact or of the trench, it is not easy to fill the three-dimensional structure completely. This phenomenon becomes more serious with the shrinkage of the minimum feature size of the semiconductor device.
Broadly stated, the typical multilayer IC electronic component is built up from a number of layers of a dielectric material layer such as silicon dioxide, fluorinated silicon oxide, polymers including polyimide and fluorinated polyimide, ceramics, carbon and other dielectric materials. In the processing sequence known in the art as the “Damascene Process”, the dielectric layer is patterned using known techniques such as the use of a photoresist material which is exposed to define the wiring pattern. After developing, the photoresist acts as a mask through which a pattern of the dielectric material is removed by a subtractive etch process such as plasma etching or reactive ion etching. Using the Damascene Process, openings defining wiring patterns are provided in the dielectric layer, extending from one surface of the dielectric layer to the other surface of the dielectric layer. These wiring patterns are then filled with a metal using a filling technique such as electroplating, electroless plating, chemical vapor deposition, physical vapor deposition or a combination of methods. This process typically includes planarization of the interconnect metal by removing excess metal with a method such as chemical mechanical polishing or planarization. In the Single Damascene Process, vias or openings are provided in the same dielectric layer and filled with metallization to provide electrical contact between layers of wiring levels. In the Dual Damascene Process, the via openings and the wiring pattern openings are both provided in the dielectric layer before filling with metallization. This process simplifies the procedure and eliminates some internal interfaces. These procedures are continued for each layer in the electronic component until the electronic component is completed.
In FIG. 5, a dual Damascene line of the prior art is shown connecting two conductor containing dielectric layers. Dielectric layers 31 and 38 contain metallization 32 in layer 31 and metallization 39 in layer 38. A stud 36 and trench 40 are shown encased by a wall 34 of a diffusion barrier liner. It is this type structure which has been shown to contribute to an interconnected electronic component having a low electromigration life.
The dielectric material provides electrical insulation and electrical isolation between the copper wiring elements. The openings in the dielectric layer typically called vias, when filled with a conductive material, are typically referred to as studs. The studs and a trench for a dual Damascene structure provide the vertical interconnections between the horizontal copper metallization on the various layers of the electronic component.
To avoid metal diffusion between the metal and the dielectric, barrier layers, also referred to as liners, are included in the structure to contain the copper or other metal and to provide improved adhesion of the copper lines and studs to the dielectric or other metallization.
Bearing in mind the problems and deficiencies of the prior art, it is therefore an object of the present invention to provide a multilayer electronic component including components made by using a single Damascene process or a dual Damascene process comprising at least one layer having through openings which are filled with a conductive material to form a trench and/or stud which trench and/or stud electrically connects metallization on other layers and which trench and/or stud has excellent step coverage, uniformity, low resistance and adhesion to CVD-copper.
It is another object of the present invention to provide a method for making a multilayer electronic component having trench and/or stud interconnections including components made using a single Damascene process or a dual Damascene process wherein the trench and/or stud have excellent step coverage, uniformity, low resistance and adhesion to CVD-copper.
A further object of the invention is to provide an interconnect structure in an electronic component for connecting metallization on one layer to metallization on another layer with the interconnect having excellent step coverage, uniformity, low resistance and adhesion to CVD-copper.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.